LONDON (Reuters) - Britain's High Court has quashed a legal challenge against the detention under anti-terrorism laws of the partner of journalist Glenn Greenwald, who brought leaks from former U.S. spy agency contractor Edward Snowden to world attention.

David Miranda had appealed against his detention and nine-hour questioning under anti-terrorism legislation last August when he landed at London's Heathrow Airport en route from Berlin to Rio De Janeiro, Brazil.

British authorities seized items from Miranda which they said included electronic media containing 58,000 documents from the U.S. National Security Agency, Snowden's former employer, and from its British counterpart, Government Communications Headquarters (GCHQ).

The High Court ruled on Wednesday that the detention of the partner of the ex-Guardian newspaper reporter was lawful.

"In my judgment the Schedule 7 (of the Terrorism Act) stop was a proportionate measure in the circumstances," said Judge John Laws.

"Its objective was not only legitimate, but very pressing."

(Reporting By Costas Pitas; editing by Stephen Addison)

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